The present invention relates, in general, to an air-cooled multi-cylinder, two-stage air compressor and motor combination for a railway locomotive and, more particularly, the present invention relates to a crankshaft of such air compressor driven by an electric motor being supported by an external bearing.
It is well known that multi-cylinder air compressors are used on freight and passenger locomotives to supply compressed air to the operating and control equipment of a railway air brake system. Many of these prior art air compressors have a pair of low-pressure cylinders and a high-pressure cylinder mounted on and supported by a crankcase in the usual manner and contain pistons which are actuated by connecting rods driven by a rotary crankshaft. One end of the crankshaft is coupled with and driven by a suitable rotatable prime mover, such as an electric motor. The other end of the crankshaft is keyed and thread ably attached by a locknut to the hub and wheel of a cooling fan assembly.
There are advantages of having the compressor directly driving the cooling fan. When the demand and speed of the air compressor increase, the speed and cooling capacity of the fan is proportionally increased. The fan can only stop turning when the compressor stops working or ceases to rotate. It has been found that the use of a separate electric motor for driving the cooling fan is unreliable since failure of the motor would result in the loss of the cooling effect and could allow the temperature of the rotating compressor to rise to dangerously high levels which could cause deterioration of the lubricating oil and could result in seizure of the air compressor.
The crankshaft driven by the electric motor does not, in prior art, have any support on the motor end of the shaft. This is the opposite end of the shaft from the fan. As the shaft rotates, in time, it may tend to vibrate and may possibly wobble. Any movement of the shaft, other than the rotatable movement which it is designed to have, may cause problems with the motor.
Proper operation requires that there be a space between the stator and the rotating portion of the motor. This space must be maintained. If the rotor contacts or rubs against the stator, problems with the motor may occur. On the other hand it is also important to keep the space between the stator and rotor to a minimum because as the space increases there is a loss of efficiency and of the power of the motor. Thus, the space is necessary but it must be kept as small as possible. When the shaft vibrates or wobbles it may cause the rotor to rub against the stator and, thus, adversely affect the motor.
The present invention provides an external mount assembly for supporting a rotatable shaft member driven by an electric motor. The external mount assembly comprises an annularly projected bearing support member being disposed in a substantially vertical plane and a bearing member secured on the bearing support member. Such bearing member is aligned with one end of a rotatable shaft member that is the opposite end of a rotatable shaft member connected to the hub and wheel of a cooling fan of such air compressor. Wherein the bearing member is used for supporting such rotatable shaft member thereby reducing extraneous vertical and horizontal movement of such rotatable shaft member while permitting such rotatable shaft member to rotate freely.
A second embodiment of the invention provides that in combination with a multi-cylinder two-stage air compressor in which an electric motor is used to drive a rotatable shaft member of said air compressor, there is an external mount for supporting the rotatable shaft member of the air compressor. Such external mount comprises an annularly projected bearing support member disposed in a substantially vertical plane and a bearing member secured on the bearing support member. Such bearing member is aligned with one end of a rotatable shaft member that is the opposite end of a rotatable shaft member connected to the hub and wheel of a cooling fan of such air compressor. Wherein the bearing member is used for securing the rotatable shaft member thereby reducing extraneous vertical and horizontal movement of the rotatable shaft member while permitting such rotatable shaft member to rotate freely.
It is, therefore, one of the primary objects of the present invention to provide a support for the crankshaft external to the motor housing in an air compressor/electric motor combination so as to reduce any vibration of the shaft.
It is also an object of the present invention to provide an outside support for the crankshaft in an air compressor/electric motor combination so as to reduce the possibility of the rotor rubbing against the stator.
An additional object of the present invention is to provide a support for the crankshaft in an air compressor/electric motor combination that is mounted on the housing of the electric motor.
These and various other objects and advantages of this invention will become apparent after a full reading of the following detailed description, particularly, when read in conjunction with the attached drawings as described below and the appended claims.